Green algae - Oocystis
The genus Oocystis is making spores within the cell wall. The picture shows three elliptic auto-spores inside the thick cell wall of the mother cell. The auto-spores will be liberated by brake of the mother cell wall.
O.lacustris has elliptic cells and elliptic spores inside. O. lacustris is one of the most common species in water poor with nutrients.